1. Field of the Invention
This invention relates to the transfer of liquids from a vessel offshore, to an onshore storage facility. More particularly, the present invention concerns a method and vessel for transferring large quantities of liquids, primarily refined hydrocarbons, from large tanker vessels offshore to onshore storage tanks using flexible pipe that can be rapidly deployed and recovered. The flexible pipe is heavier than the water that it displaces, and of small enough outside diameter such that it does not require anchoring in place on the sea floor.
2. Description of the Prior Art
The ability to transfer liquids from a vessel offshore to an onshore storage facility is known in the prior art. Systems typically include the installation of pipe on the sea floor, and the anchoring of that pipe in place, often by burying the pipe, or by covering it with heavy mats. These installations are designed to prevent the pipe from moving in the current, including severe currents that may be experienced in adverse weather conditions. Accordingly, these installations are often permanent and require substantial time to install. The piping cannot be easily retrieved for use at another site. If the pipe can be retrieved at all, it is at great expense and time investment.
Systems designed for rapid deployment of pipe have utilized pipe that is lighter than the sea water which the pipe displaces, such that the empty pipe floats when placed into the water. It is only when the pipe contains a liquid that the pipe, containing the liquid, is heavy enough to sink to the sea floor. Such systems, while providing the means to rapidly deploy the pipe, also required the pipe to be anchored on the sea floor. If not anchored, the pipe was too light to be resistant enough to the currents to remain in place. Systems that utilize such a “float/sink” deployment method require significant attention to anchoring, or simply cannot be used in adverse weather conditions. Additionally, deploying the pipe initially on the sea surface subjected the pipe and the attendant vessels and personnel to added risks when confronted with significant waves, winds, and tides.
Furthermore, systems requiring that a liquid be placed in the pipe to make the pipe heavy enough to sink create a potential liquid disposal problem and increase the risk of an environmental spill. Systems using sea water in the pipe in a “float/sink” deployment, may be confronted with a substantial quantity of contaminated sea water if the pipe still contains hydrocarbon residues from a prior use. Systems which utilize the liquid to be transferred (petroleum or other hydrocarbons) to give the pipe the required weight in a “float/sink” deployment, run the risk of a spill of that liquid during deployment, and the associated environmental hazards and clean up.
The prior art does not include a rapidly deployable and retrievable system for transferring liquid from an offshore vessel to an onshore storage facility that does not require anchoring of the retrievable piping system on the sea floor. The prior art also does not disclose a rapidly deployable and retrievable system for transferring liquids from an offshore vessel to an onshore storage facility that avoids the environmental hazards associated with systems that depend upon the weight of a liquid in the pipe during the deployment process.